A hybrid vehicle incorporating an engine and an electric motor as a driving source is known. The hybrid vehicle has a power storage device such as a battery to store electric power to be supplied to the electric motor. The battery is charged with electric power generated by a power generator driven by the engine, electric power regenerated with the electric motor during deceleration of the vehicle, and the like.
Such hybrid vehicle can run using either one or both of the engine and the electric motor as a driving source depending on an operating state and the like of the vehicle. Thus, when an accelerator pedal position is small, for example, the engine is stopped, and the vehicle can run using only the electric motor as a driving source. When sudden acceleration is required, on the other hand, the engine is driven in order to obtain desired acceleration.
A running state where the engine is stopped and only the electric motor is used as a driving source involves no exhaust gas emissions, thus imposing only a small environmental load. In a hybrid vehicle, however, stopping and starting of an engine may be repeated as described above. As a result, the engine may be stopped before the completion of warm-up of the engine, which may result in frequent restart of the engine before the completion of warm-up. As is well known, when an engine is started before the completion of warm-up, a relatively high amount of HC or CO may be exhausted.
In view of such problem, Japanese Patent Laying-Open No. 2010-188935 (PTL 1) proposes to warm up an internal combustion engine until the temperature of a catalyst reaches a first temperature while an electric run preference mode is set, and warm up the internal combustion engine until the temperature reaches a second temperature lower than the first temperature while a hybrid run preference mode is set.